A carpenter brought this battery charger to my shop to be fixed. He told me that sometimes this charger works fine and sometimes it does not. When I powered up the charger, nothing came on and when I checked the output voltage in the battery holder, there was no voltage present there indication a problem in the charger.
I recalled what the man said about the charger sometimes it works and sometimes it does not and I thought to my self, this could be a problem of cold soldering joints or some bad components, in my mind I was thinking capacitors, or it could be both.
I opened the charger and checked with the naked eye to see if there is something bad showing but there was none. I checked with a magnifying lens and I could not see any bad joints. I powered up the charger and checked the voltage on the main capacitor and I got a reading of 300 volts but not steady reading. I traced it back to the main ac outlet connectors and found out that the main AC wire is not in good condition. I replace that wire and tested again. This time I was getting a steady 300 volts on the main capacitor legs but still no indication of any power present beyond the main the primary power section.
A friend of mine brought this LCD projector to my shop. He said that this LCD projector was kept in the storage room for over a year and when they wanted to use it again, it kept shutting down after a few seconds of operation.
I plugged it in and I could see the power led changing from orange to green but the green kept flashing and the light of projector came on for a few seconds, then it shut down. From what I saw, the main problem was either in the power supply area or in the cooling area of this device.
I took four screws out and the top of the machine came off. I turned it on and sure enough, it started to come on but it shut down again but I noticed one of the cooling fans was not working. It was trying to start but it did not.
There were three fans in the machine, two fans for the power supply and one for the main light. The fan that did not work was the one near the power supply that cools down the main section of the power supply. I turned the machine on again and before it shuts down, I checked the voltage at the socket of the fan and there was 12 volts present at the socket which is an indication of a bad fan on board.
I took the fan out and tried to spin it by hand but it did not spin. I cleaned it with an air blower and a lot of dust came out then I spread it with a contact cleaner and spun the fan again, this time, it started to spin.
I put it back on the board and tuned the projector on. All the fans started to spin and the light came on for a while. I plugged in a video source and I could see that source projected on the wall.
I kept it on for almost an hour. Called the customer and got his machine back with a big smile on his face. It was worth the time and the effort.
A Wii play station with an external power supply was brought to my shop with the problem, a dead play station. I plugged it in and the play station did not come on, not even a stand by light was present. I unplugged the external power supply and checked the power there and realized that there was no power coming out of the external power supply. Well, let the repair begins.
The moment I opened the cover of the external power supply and scanned the components on board, I could not see anything wrong. I took the board out and checked the main capacitor, there was 300 volts reading which indicates a problem in the power supply because the main capacitor was holding the charge. There is a component beyond this point that is not allowing the power to go through that is why the main capacitor is still holding the charge. I discharged the main capacitor and checked with LOPT/FBT tester and it gave me a full bar indicating that the main capacitor, the MOS N FET and the diodes in the secondary area of the power supply are ok.
I plugged it in the electricity outlet and started checking with the voltmeter and I found a resistor that is on the same line with the main capacitor that was open. I could get a reading on one side of the resistor and there was no reading on the other side of the resistor. It was a 220 K ohm resistor that was open and not letting any power to go through.
I discharged the main capacitor again and soldered that resistor out and replaced it with 220k ohm resistor and when I plugged it in, I could read 12 volts coming out of the external power supply. When I plugged it in the back of the Wii station, it came on and I could see the stand by light changing from a red stand by light to a green ready light.
I put a game CD in the try of the play station and enjoyed playing a football game for about an hour. It was lots of fun but mostly was happy that it worked.
This LCD computer monitor was brought to me and the complaint was, a dead LCD with a flicking on and off stand by light. It had an external power supply and the moment I turned it on, a green stand LED start flashing on and off. I tested the external power supply and I could see a reading of 18 volts. To make sure that the external power supply was working fine. I add a 24 light bulb (car light bulb) to the socket of power supply and I could see the light bulb coming on steady which is an indication of a working external power supply.
Upon opening the LCD monitor cover, I headed directly to the power board inside and scanned the area looking for something bulged or burnet but I could not see anything like that. With the ESR meter, I checked all the capacitors on that board and found four bad ones that went high in ohm causing the LCD monitor not to work. Usually, I find bad capacitors inside but sometimes when replacing these bad capacitors, I find other problems with either the back lights or the inverter board.
This LCD monitor, came with a separate inverter board and it has only two small tiny capacitors on it and both of them checked fine. I checked the back lights in the LCD monitor and all of them checked ok. So hopefully nothing else is bad in this monitor.
I replaced all the bad capacitors on the board which were found in these locations:
After replacing all of these, I powered up the LCD monitor and I saw it coming to live with nice vivid colors. I connected it to my laptop and let it run for more than one hour and it worked very nicely.
A lot of people come to my shop asking me if I can repair electronic welding machines and I have no clue how to do that, I have no clue how they work therefore I can not fix them. This time I was eager to find out how they work and how I can repair them. A guy who knew my brother came to my shop asking me to repair this electronic welding machine for him.
The moment I turned it on, I could hear the fan running, so I opened the cover and took a look inside to see what I am dealing with. There were about three electronic boards there and components that I am very familiar with. I took it next door to my brother workshop (my brother uses this kind of machines so he is very familiar with it). He hocked up the welding cables and tried to weld with it but it did not work, there was a red LED on board that was on but flickering and the green power led was not on which gave me the indication that there is something wrong with the power supply.
I took it back to my work shop, took the power board off and started testing. I noticed the main capacitor was holding the charge. I discharged it and started testing the component around it. I tested it with a LOPT/FBT meter and it did not give me full bars so I was suspecting some bad component like diodes, main capacitor and MOS N FET some where in the area. After some testing I found a diode that was shorted out in the secondary side of the power supply. It was market with HER 206, so I replace that with HER 203 and tested again with LOPT/FBT and still did not get full bars on it. I noticed that the main capacitor was starting to bulge just a little bit. It was 47uf/400 volts so I replaced that with a new one. When tested with the LOPT/FBT meter, it was not give me full bars yet and when I turn the machine on, the main capacitor was still holding charge. After a deep checking with a strong magnifying lens, I found out that there is a line on the opposite side of the board that connects the main capacitor positive leg to the MOS N FET was not soldered right and I thought that is why the main capacitor was holding the charge.